add workflow to rebuild the site + push output folder to netlify

.github/workflows/rebuild-and-publish-to-netlify.yaml

@@ -0,0 +1,32 @@
+# Builds the site on GitHub because GitHub offers 2000 free CI/CD minutes, while Netlify offers 300.
+# See: https://bennypowers.dev/posts/cheap-netlify-11ty-rebuilds/
+
+name: Rebuild Netlify site
+
+on:
+  push:
+    branches:
+      - main
+
+jobs:
+  rebuild:
+    runs-on: ubuntu-latest
+    name: Rebuild site
+    steps:
+      - uses: actions/checkout@v3
+      - uses: actions/setup-node@v3
+        with:
+          node-version-file: '.nvmrc'
+          cache: 'npm'
+      # use cached node_modules if found (instead of running npm install)
+      - run: npm ci --prefer-offline
+      - run: npm run build
+
+      - name: Publish to Netlify
+        env:
+          # Netlify settings "Site name"
+          NETLIFY_SITE_ID: ${{ secrets.NETLIFY_SITE_ID }}
+          # Netlify personal access token created here: https://app.netlify.com/user/applications
+          NETLIFY_AUTH_TOKEN: ${{ secrets.NETLIFY_AUTH_TOKEN }}
+        # Deploy updated "_site" folder to production Netlify branch
+        run: npx netlify-cli deploy --prod --message "deploy from GitHub Action" --dir=_site